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Power management : Linux Mint 20.3 and new P15 Gen 2 Thinkpad

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Power management : Linux Mint 20.3 and new P15 Gen 2 Thinkpad

#1 Post by donzo » Sun May 22, 2022 5:37 pm

Hi all, I got my new P15 Gen 2 thinkpad, very exceited. First thing I did was wiped the windows and installed Linux Mint. Initially WIFI did not work but I upgraded the kernel to 5.13 and that was fixed. So far everything about the laptop is great except...

.. the battery power is terrible. On a full battery charge it says it will last less than 2 hours. I tried installing "tlp" and played with it a little bit but didn't make any difference.

I am hoping that I am making some simple mistake, like I need to install a power management driver or package. I haven't contacted Lenovo support yet, thought I would start here.

If anyone has ideas of how to manage the power on my new awesome laptop, I would greatly appreciate it.

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Re: Power management : Linux Mint 20.3 and new P15 Gen 2 Thinkpad

#2 Post by mikemex » Sun May 22, 2022 6:46 pm

Don't know about Mint. I use Ubuntu. But it should be similar.

Get powerstat and powertop.

With powertop run (with sudo) the 'powertop --calibrate' command. It'll take a while but it'll help you determine what's consuming power.

Once done, run powertop again and hit TAB to cyclle through its menus. In adjustables, it should show which devices could be tuned.

It also lets you know which power states are available and how they are used.

On my P14s Gen 1 AMD I've determined that I have a small leak (about 0.5W) with ethernet not powering down (Realtek r8169 driver) and the touchscreen (about 0.5W). I disable the connection manually with 'ip link set xxxxx down'. For the touchscreen, I use powertop, but it can be done with a simple echo to the proper device.

Also, for some reason, the AMD chip doesn't have deeper C states. It shows up to C3. The 6600U in my X1C4 offers up to C10.

There is no way to save power without reducing performance or functionality, other than undervolting. What power management usually does is to detect idle time and put the device into a state of minimal consumption during such periods. But if you're using the machine, the only way to reduce power is to limit the level of performance or the features you have enabled. With power you can't have the cake and eat it too. So if you want your laptop to last longer on battery, consider limiting the CPU frequency to lower levels only. With a P15 that shouldn't be much of a sacrifice.

Disable turbo. Turbo not only shortens the battery life; it degrades its life as well. The faster you drain a battery, the more heat it produces and heat kills batteries.

Also, try disabling the discrete graphics card in the BIOS. For reference, my W530 consumes 22W idling with the dGPU enabled and 9W disabled.

Its a big screen so lower your screen brightness. I've noticed that readability is much better in dark mode.

There is also the possibility that the P15 G2 uses devices that Linux don't know how to handle properly yet. I know the fingerprint sensor in my machine still isn't recognized.

Linux runs better on my X1C4, perhaps because it's older. But it always has quirks (suspension, for example, doesn't always works; sometimes it hangs and never wakes up).

Use the 'powerstat -d (delay)' command to get statistics of battery usage.

T61: T8300 | 8GB | 400GB S3610 | SXGA
X301: SU9600 | 8GB | 400GB S3610
T420s: 2640m | 16GB | 400GB S3610 | HD+ 4200M
W530: 2740qm | 32GB | 400GB S3610 | FHD K1000M
X1C5: 7600U | 16GB | 1TB PC711 | FHD
P14s G1 AMD: 4750U | 32GB | 1TB PC611 | PG FHD Touch
T14 G2: 1145G7 | 32GB | 1TB PC711 | FHD

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